3 forum posts
National Geographic Topo Question
3 forum posts
Topo does not provide the grid north deviation. You don't really need it anyway for using your baseplate compass with the printed maps. The neat line (the edge of the printed map) on the east and west sides is true north-south. So when using your compass with the map to translate your magnetic bearings to and from the map, you simply use the compass in its protractor mode (one of the important reasons to use a baseplate compass rather than any other type), checking the angle with the neat line. If you are getting the bearings from the computer, Topo automatically gives you the magnetic bearing, using the current value of the magnetic declination, so no conversion is needed. Remember, you will be using the compass in the field, so you only need the magnetic bearing, not the grid and not the true bearing. If you do need to translate to or from the map, just use the T to M translation using the map N-S neatline, as I already said.
I realize that you are trying to make the determination using the UTM grid you print on the map. But it is just as easy to use the neat line, or to use a lat-lon grid to provide the true N-S reference line.
People for some reason believe that UTM is easier to use than lat-lon, because it is a "square" grid. They have been told that lat-lon lines are "curved". However, on the scale the backpacker is going to use, lat-lon is a rectangular grid. The "curvature" is a result of forcing the Earth's curved surface onto a "flat" map. UTM grid lines are in fact much more curved, and only appear "straight" because they are printed on a flat piece of paper and the Earth's features are distorted to match the flat paper. Remember, UTM stands for Universal Transverse Mercator. Remember those maps in your school classroom that show Greenland as bigger than the rest of North America? That's a Mercator map.
And no, you do not need to know any spherical trigonometry to use lat-lon for hiking on a map.
For those of us who realized long ago that UTM is useful only for small areas and has some significant flaws, the coordinate system makes no difference. Whatever the coordinate system (lat-lon, UTM, State Plane, Range-Township), a coordinate system is only an address system. If you can find your way to an address in a city, you can use any one of the systems. Remember that UTM was devised for military usage, primarily for draftees and recruits many of whom had not graduated from high school, with much of the usage being for artillery, mortar, and machine guns ("your target is 350 meters east and 220 meters south of your position"). Other problems include the significant discontinuities at zone boundaries and the variation in the grid angle across even a 7.5 min quad. Here in California, the boundary between zones 10 and 11 (the 120 deg west longitude line) happens to run right through some of the more popular backpacking parts of the Sierra (middle of Lake Tahoe, Mokulmne Wilderness, just west of Yosemite NP), crossing the PCT in the Carson Pass and Luther Pass area. The Zone 11-12 boundary runs through Missoula, MT, and along the Utah western border, as well as some of the more interesting hiking parts of Glacier NP and not far from Great Basin NP. In the East, the 18-19 boundary runs through western NH and almost through Sturbridge Village, MA.
82 forum posts
As amazingly easy as MGRS (UTM, basically) is, people still mess it up. Guys trying out for Army SF have been known to walk a back azimuth when trying to dead reckon. One thing I've noticed with navigation, is it's hard to let go of the way you're first taught. I'd imagine Big Sky was taught in the military, or by military.
Bill, I've used MGRS (and terrain association, of course) to find a person sleeping on the ground from over 15k away, as well as to navigate over entire countries. I'm sure you know about its flaws a lot more than I do, but I've never found its use to be limited to small areas.
I've used MGRS (and terrain association, of course) to find a person sleeping on the ground from over 15k away, as well as to navigate over entire countries.
15k is a small distance. I'm not sure what the "entire countries" are, though there are lots of countries in the world that are under the 15k size (but, as I have found, don't insult the citizens by implying that their country is unimportant because it is small - some of them take huge umbrage at such an implication).
Anyway, as long as you stay within a zone, or are aware of what happens at the boundaries, UTM is easy (for those who might be confused by rdavis' reference to MGRS in a discussion of UTM - MGRS = Military Grid Reference System. This is a further simplification of UTM, in which the leading digits of Easting and Northing are replaced by letters). A zone is 6 deg wide in longitude, which is about 331 miles at my latitude, 414 miles at the equator, and 207 miles wide at the latitude of Anchorage. When you get far enough north or south, UTM doesn't work at all, and you have to use the UPS (Universal Polar Stereographic) system, in which the square grid system doesn't match N-S or E-W except for 2 lines corresponding to the 0-180 deg longitude great circle and the +90 to -90 deg longitude great circle. UPS is used basically north of 84 deg N and south of 80 deg S latitudes, so doesn't affect most people. UPS does avoid the singularities of the N and S Poles that the lat-lon system has.
As for BigSky's being taught UTM/MGRS in "the military", better specify which "military", son. The Navy teaches lat/lon (the Real Man's coordinate system, if you ask an old Navy man - but of course, if you ask a Navy person, man or woman, the Navy is the only Real Military). Ummm, well, the Marines teach UTM. Of, and the Air Force teaches lat-lon. Basically, the reason is that lat-lon more accurately represents the Earth, and has no discontinuities.
But, when you come right down to it, if you are using a GPS receiver, or are on the computer using a mapping program like Topo, it doesn't really matter which coordinate system you use, as long as you specify it, along with the datum. The GPSR and the computer do all the figuring for you (and for some of us, our PDA or Smart Phone will display the maps and figure out all the coordinate business).
I agree that people tend to stick with what they first learned, at least until they get into a situation where it makes a real difference. If you have to travel over the distances that a blue-water sailor or an airman travels, UTM is awkward at best. If you are lobbing artillery shells, UTM is easier to work between spotter and gunner. If you are on foot or in a tank, it's often easier to know you are to travel so many km east and so many north (or west and south, which is just the reverse, and you call them "clicks" instead of kilometers) than going from a lat-lon to another lat-lon (except that your GPSR will tell you to follow a bearing for a distance, regardless of the coordinate system you used to feed in the destination). Hey, guess what! Bearing and distance is a polar coordinate system, just like lat-lon! And you could say that over short distances you follow the straight line on the map, which becomes a great circle or a rhumb line if you go far enough.
Oh wait, you cheated! You used terrain association, not just MGRS! Which is, of course, the proper way for a backpacker to navigate. You can't follow a bearing very far in real terrain. You have to adjust for terrain.
When you come down to it, the coordinate system doesn't matter, as long as you are consistent. When you go to different countries, you have to be prepared for different coordinate systems on their maps (unless you are using NIMA maps).
23 forum posts
As I have said before I am new at all of this. With that out of the way, which system should someone learn if they have never learned any of these navigation methods before? Honestly I am not sure I can properly use a compass. I have tried searching for a class or something like that in the Alabama area, but I am not sure what I should even be looking for. Is there anything or one who teaches this material, if so where can they be found? This summer presents a lot of opportunity for me to get out on the trails and I would like to take full advantage of it, preferable without getting lost. As always thanks for you help!
1,251 forum posts
For me the easiest method of navigation is using the topo map with it's printed utm coordinates. You don't even need a grid overlay.
With your gpsr set to use utm, you can easily project where you want to go by eyeballing and get yourself within 100 yards of where you want to go.
Learn to read terrain first, then learn to read topographic maps (what do all those multi-colored lines mean, anyway - blue, brown, black, green patches, ...), and then learn to relate the map and terrain to each other. The best way to do this is get topo maps of the area you are in or going to (NW Alabama has some interesting terrain that will include most of the important types of features) and get out there with the map in hand. Let me emphasize - MAP IN HAND!!! not tucked away in your pack. Keep following on the map continuously where you are. Follow trails at first (being line features, it is fairly easy to track your location - follow the turns in the trail, and note surrounding features - branch streams, hills, etc). And keep the map oriented as the ground lies (too many people hold the map with the north edge "up", rather than matching the ground). Find some high places and sit for an hour or two at each matching the map and terrain.
There are a number of good books that will lead you through the basics, although there are organizations that do hiking and orienteering that will teach you. Look at the land navigation books from The Mountaineers Press, National Outdoor Leadership Schools (NOLS), etc (you can search on Amazon).
Orienteering is an excellent and fun way to learn matching map to terrain. Look on the US Orienteering Federation website http://www.us.orienteering.org/. There is an orienteering club in Alabama - Vulcan Orienteering Club (VOC) - c/o James Pilman, 2875 Blackjack Rd., Trussville, AL 35173. 205-437-0550 (Ka4zqa at aol.com). Their website is http://home.earthlink.net/~ciza/voc.html. They will be glad to teach you all about map and compass, and for free (except for the entry fee to their events, which basically pays for the map). They have upcoming meets at Oak Mountain State Park, just south of Birmingham, on Apr 19 and May 17.
After you learn to match map and terrain, then learn how to use the compass (actually pretty simple, but too many people teaching compass complicate it with magic formulas about declination, where in fact there are simple, intuitively obvious ways of dealing with that). Frankly, in all the years I have been wandering the woods, hills, deserts, tundra, and "frozen wastes" on 6 continents, I have rarely used a compass except for rough orientation of the map (and there are very few places in the world where you need to worry about the magnetic declination for that). As I have posted here before, I have only gotten lost once in my life, at age 5, wandering around Tegucigalpa by myself. And yes, I do know how to use a compass, surveyor's transit, sextant, various radio-navigation devices, and GPS (I worked for about 10 years on various aspects and applications of the Global Positioning System) - wonderful devices all, but only as aids to navigation, not substitutes for knowledge and experience.
After you have gotten comfortable with map and compass, then, and only then, should you even consider getting into coordinate systems. Coordinate systems are really unnecessary for 99% of what the backpacker or hiker does. As I said in my previous post, coordinate systems are just an address system. It really does not matter which system you use (and eventually you will need to be familiar with both UTM and lat-lon). Whether you use lat-lon or UTM (MGRS or one of the country-specific variants), you just measure E-W and N-S. Some maps are cluttered up with a UTM grid overprint, which does sometimes make UTM coordinates more convenient (note that I did NOT say "easier"). If you use a computer program like NatGeo's Topo!, you can get the coordinates by pointing to the desired location and either reading off the position or clicking to mark a waypoint to download to your GPSR - no need to measure (you can also load the map to a PDA and do the same thing). For a paper map (which I recommend you should always carry), you can print the map with either a lat-lon grid or a UTM grid. I don't really recommend this, since it just adds more clutter to the map.
23 forum posts
Bill - Thanks a million
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